Automatic camera-based driver assistance systems capture the vehicle surroundings using at least one camera, interpret the image data obtained, and use it to determine a system-specific response from it. Interpretation of the vehicle surroundings includes the detection of luminescent or illuminated elements of the infrastructure or of road traffic. Examples are traffic lights, traffic signs, headlights, and tail lights.
Use of LEDs (light-emitting diodes) instead of light bulbs as lamps presents a greater challenge to camera-based driver assistance systems. Such LEDs are typically not operated continuously but switched on and off in pulsed mode. This means that they are not constantly lit but emit a rapid sequence of light flashes which, due to the slowness of the human eye, is perceived as constant lighting. Such pulsed light sources or light sources operated in pulsed mode can be problematic for camera-based driver assistance systems. One effect can be that the individual images taken by the camera(s) do not show all the information the human eye perceives as illuminated but just parts of it or, in extreme cases, none of it.
Document WO 2011/091785 A1 shows a highly dynamic image sensor for detecting modulated light. The number of charge carriers that can be collected by the pixels of the image sensor can either be reduced or increased starting from an initial number, for example by switching capacitors or resistors provided for that purpose on or off.
In such a solution however, the hardware and control of the image sensor have to meet special requirements, making it more expensive than a standard image sensor that is already used in driver assistance cameras.